Centrifugal pump provided with diffuser



I Sept 28, 19489 e. P. E. HOWARD ET AL A Q CENTRIFUGAL PUMP PROVIDED WITH DIFFUSER 2 Sheets-Sheet 1 Filed Aug. 2, 1946 Sept. 2%, 1948. G. P. E. HOWARD ET AL A Q CENTRIFUGAL PUMP PROVIDED WITH DIFFUSER I 2 Sheets-Sheet 2 Filed Aug. 2, 1946 Patented Sept. 28, 1948 TENT OFFICE .iCENTRIFUGAL PUMP 'PRGWI DED WITH DIFFUSER .Giles 'PhllipEliot Howard and Alexander "Ivanoff, 'Luton, England Application August 2, 1946, Serial No. 687,824 In GreatBritain July 11, 1945 Section 1, Public Law 690, August 8,1946 Patentexpires July 11, 1965 6 Claims.

This invention relates to centrifugal pumps provided with diffusers. In centrifugal pumps, the liquid issues from "the outer .periphery of the rotor or impeller at high velocity, and a diffuser is a device which immediately surrounds the impeller and isadaptedto receive the'issuing liquid and gradually reduce thevelocity, andtherefore increase .the pressure; thereof The diffuser generally consists of a stationary integral annular casting surrounding the :impeller and having front and backannular wallswhose inner edges are immediately outside the ,outer edges of the front and back annular :walls of the impeller. Theannular walls of the :diffuserhave between them a number of arcuatevanes arranged somewhat similarly to the arcuate vanes between the annular walls of .thezimpeller :but in the opposite sense.

The present invention has for its object the provisionofan improved construction of centrifugal pump :provided with a diffuser, which will both simplify .the :assemblyand enable a closer clearance to be obtainedibetween the diffuser and the impeller without danger of seizing. In accordance with .the invention'the diffuser is fr to adjust .itself relative to the p mp casing and is held imposition by being biased against a fixed abutment.

In order that the invention may be the more clearly understood, a pump structure in accordance-therewith will :now be described, reference being made to the accompanying drawings, wherein:

Figure 1 is a sectional .side elevation of said pump structure.

Figure 2 is a cross section on line 11-11 of Figure 1.

Referring to-the drawings the pump structure illustrated therein is identical with that ,described and illustrated in ounce-pending U. S. applicationSerial No. 687,823, filed of even date herewith, Figure 1 being identical with the single figure of said co-pending specification. Only so much of said structure which specifically relates to the present invention will therefore be described.

Thus the pump impeller I is mounted on the lowermost end of a vertical shaft 2. The impeller l is located within a pump casing 3. The liquid enters the impeller l .axially in the usual way through a port 4 in the bottom wall of said casing 3 and flows outwardly from the impeller into a surrounding annular space 5 in the casing 3 and from said space '5 flows radially out through an outlet port 6.

The impeller l in the usual wayis'an integral casting consisting of .two concentric disc-like walls 7 and 8 with aplurality of curved vanes 9 between them. The lower '1 of said disc-like walls has a central opening surrounded by a flange it which rotates in sealed relation within the port 4 and thus the liquid is admitted into the impeller. The upperS of said disc-like walls is rigidly secured to the shaft 2.

Surrounding the outer periphery of the ,im peller is a stationary diffuser. This is an integral casting consisting of lower and upperannular walls H and I2 with curved vane 13 between them. The inner edges of the walls II and I2 closely surround the outer edges of the walls 1 and 8, and the vanes H are curved in the opposite sense to the vanes 9. As shown, the aforesaid annular space 5 immediately surrounds the dif fuser and the liquid flows through said diffuser from the impeller to the said annular space, and. in passing through said diffuser has its velocity head converted into pressure head as heretofore stated.

In the present construction the impeller l is formed with a central boss 14 extending from its upper wall 8 in a direction away from the pump inlet. The diffuser is cast with anintegral web IS in the form of a dished disc whose outer edge joins the upper annular wall l2 of said diffuser, and which has a central bossed opening which surrounds, and bears upon, the said boss M of the impeller. In this way correct axial alignment of the diffuser relative to the impeller is ensured.

For ensuring the correct axial positioning of the ,diffuser, an upper surface l6 of the diffuser is adapted to abut against a surface of the casing above it as shown. The diffuser is forced upwardly by the differential pressure of the liquid being pumped, and thus its said rear surface i8 is held hard up against the said surface of the casing behind it. To minimize leakage between the lower annular wall of thediffuser and the corresponding bottom wall of the casing, said lower annular wall of the diffuser may have a number of circular ribs 11 extending from it with their front edges very close to said bottom wall of the casing. Thus a species of labyrinth is provided through which any leaking liquid must pass.

The invention is particularly useful in the case of pumps handling liquid of high temperature, and, in the arrangement being described, is employed, as before stated, in combination with the exact construction described in our co-pending application aforesaid. The abutting surface l6 f the diffuser is constituted by the upper edge of a circular rib extending upwardly from the upper wall of the diifuser as shown and the corresponding surface of the pump is the lower surface of the upper portion of said pump casing.

The aforesaid differential pressure pressing the diifuser upwardly exists by virtue of the fact that the pump inlet is in direct communication with the upper side of the diffuser by way of holes [8 through the boss M. The underside of the difiuser, at the region of the ribs I! is in leakage communication with the relatively high pressure liquid in the annular space 5.

What we claim and desire to secure by Letters Patent 151 1. In a centrifugal pump comprising a fixed pump casing and a pump impeller rotatably mounted within said casing, said impeller having a central axially open liquid intake and having means for ejecting the liquid radially outwardly therefrom, a stationary diffuser surrounding said pump impeller within said pump casing and adapted to receive the ejected liquid, said diffuser being free to adjust itself relative to said pump casing and being biased against a fixed surface associated with said pump casing to hold the diffuser in position. 7

2. In a centrifugal pump comprising a fixed pump casing and a pump impeller rotatably mounted within said casing, said impeller having a central axially open liquid intake and having means for ejecting the liquid radially outwardly therefrom, a stationary difiuser surrounding said pump impeller within said pump casing and adapted to receive the ejected liquid, said diffuser being free to adjust itself relative to said pump casing and being biased by the pressure of the liquid being pumped against a fixed surface associated with said pump casing to hold the diffuser in position.

3. In a centrifugal pump comprising a fixed pump casing and a pump impeller rotatably mounted within said casing, said impeller having a central axially open liquid intake and having means for ejecting the liquid radially outwardly therefrom, a stationary diffuser surrounding said pump impeller within said pump casing and adapted to receive the ejected liquid, said diffuser being rotatable and axially movable relative to said pump impeller, and said diffuser being biased axially against a fixed surface associated with said pump casing to hold the diffuser in position.

4. In a centrifugal pump comprising a fixed pump casing and a pump impeller rotatably mounted within said casing, said impeller having a central axially open liquid intake and having means for ejecting the liquid radially outwardly therefrom, a stationary diffuser surrounding said pump impeller within said pump casing and adapted to receive the ejected liquid, said diffuser being rotatable and axially movable relative to said pump impeller, said casing defining an annular space surrounding said diffuser and having an outlet communicating with the annular space aforesaid, and means for subjecting one side of said diifuser to the pressure of the intake of the impeller and the other side of said diffuser to the pressure of said annular space, whereby said difiuser is biased axially against a fixed surface associated with said pump casing and is thereby held in position.

5. A centrifugal pump comprising a fixed pump casing, a pump impeller rotatably mounted within said casing, said impeller having a central axially open liquid intake and having means for ejecting the liquid radially outwardly therefrom, a central boss extending coaxially from the side of the pump impeller opposite to said intake opening, a stationary diffuser surrounding said pump impeller within said pump casing and adapted to receive the liquid ejected from said pump impeller, a disc-shaped web rigid with said diffuser on the side thereof corresponding to the side of the pump impeller from which the central boss extends, said disc-shaped web having a central opening which surrounds said central boss in bearing relation thereto while permitting relative rotary and axial movement between said pump impeller and said diifuser, said boss having holes extended therethrough and establishing direct communication of the intake opening of said impeller with the side of said web remote from said intake opening, said pump casing having an inlet port, means for establishing a fluid seal between the intake opening of the impeller and said inlet port, said pump casing defining an annular space surrounding said diffuser and having an outlet communicating with the annular space aforesaid, and means establishing a leakage communication between said annular space and the side of the diffuser opposite to the web for producing a net axial thrust on said diffuser serving to bias the same axially against a fixed surface associated With said pump casing and to hold the diffuser in position.

6. A centrifugal pump as defined in claim 5, wherein the means affording a leakage communication between said annular space and the side of the diffuser opposite to the web constitute a plurality of annular ribs formed on one side of said diffuser and extended close to the adjacent surface of the pump casing.

GILES PHILIP ELIOT HOWARD. ALEXANDER IVANOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 557,300 Barber Mar. 31, 1896 2,334,625 Heppner Nov. 16, 1943 

